Reapplying r5147 (caching maps for slow case objects)....

src/heap.cc

Index: src/heap.cc
===================================================================
--- src/heap.cc	(revision 5318)
+++ src/heap.cc	(working copy)
@@ -571,6 +571,22 @@
 }
 
 
+class ClearThreadNormalizedMapCachesVisitor: public ThreadVisitor {
+  virtual void VisitThread(ThreadLocalTop* top) {
+    Context* context = top->context_;
+    if (context == NULL) return;
+    context->global()->global_context()->normalized_map_cache()->Clear();
+  }
+};
+
+
+void Heap::ClearNormalizedMapCaches() {
+  if (Bootstrapper::IsActive()) return;
+  ClearThreadNormalizedMapCachesVisitor visitor;
+  ThreadManager::IterateArchivedThreads(&visitor);
+}
+
+
 #ifdef DEBUG
 
 enum PageWatermarkValidity {
@@ -755,6 +771,8 @@
   CompletelyClearInstanceofCache();
 
   if (is_compacting) FlushNumberStringCache();
+
+  ClearNormalizedMapCaches();
 }